Generally speaking, in a clutch unit using engagement members such as cylindrical rollers or balls, a clutch section is arranged between the input side member and the output side member, and, in the clutch section, the engagement members such as cylindrical rollers or balls are engaged/disengaged with/from a wedge gap formed between the input side member and the output side member, thereby controlling transmission/interruption of the input torque.
A clutch unit of this type is incorporated into a seat lifter section for a vehicle which vertically moves a seat through lever operation. This clutch unit is provided with a lever side clutch section transmitting rotational torque from the input side to the output side and a brake side clutch section transmitting rotational torque from the input side to the output side and shutting off reverse input torque from the output side (see, for example, Patent Documents 1 and 2).
FIG. 14 is a sectional view showing the general construction of the conventional clutch unit disclosed in Patent Documents 1 and 2, and FIG. 15 is a right-hand side view of the clutch unit shown in FIG. 14. FIG. 16 is a sectional view taken along the line C-C of FIG. 14, and FIG. 17 is a sectional view taken along the line D-D of FIG. 14.
As shown in the drawings, a lever side clutch section 111 mainly includes a lever side outer ring 114 serving as an input side member to which torque is input through lever operation, an inner ring 115 serving as a coupling member transmitting the torque from the lever side outer ring 114 to a brake side clutch section 112, a plurality of cylindrical rollers 116 serving as engagement members controlling transmission/interruption of the input torque from the lever side outer ring 114 through engagement/disengagement between the lever side outer ring 114 and the inner ring 115, a retainer 117 retaining the cylindrical rollers 116 at predetermined circumferential intervals, a brake side outer ring 122 serving as a stationary side member constrained in its rotation, an inner centering spring 118 serving as a first elastic member which is provided between the retainer 117 and the brake side outer ring 122 and accumulates elastic force with input torque from the lever side outer ring 114, restoring the retainer to the neutral state with the accumulated elastic force through releasing the input torque, and an outer centering spring 119 serving as a second elastic member which is provided between the lever side outer ring 114 and the brake side outer ring 122 and accumulates elastic force with input torque from the lever side outer ring 114, restoring the lever side outer ring 114 to the neutral state with the accumulated elastic force through releasing the input torque.
In the drawings, numeral 113 indicates a lever-side side plate fixed to the lever side outer ring 114 by swaging and constituting the input side member together with the lever side outer ring 114, and numeral 130 indicates a washer mounted to an output shaft 124 through the intermediation of a wave washer 131.
On the other hand, the brake side clutch section 112 mainly includes the brake side outer ring 122 serving as a stationary side member constrained in its rotation, the inner ring 115 serving as a coupling member to which torque from the lever side clutch section 111 is input, and a plurality of pairs of cylindrical rollers 125 serving as engagement members arranged in a gap between the brake side outer ring 122 and the output shaft 124, for controlling transmission of input torque from the inner ring 115 and interrupting reverse input torque from the output shaft 124 through engagement/disengagement between the brake side outer ring 122 and the output shaft 124.
A flange portion of the inner ring 115 functions as a retainer retaining the cylindrical rollers 125 at predetermined circumferential intervals. In the drawings, numeral 123 indicates a brake-side side plate fixed to the brake side outer ring 122 by swaging and constituting the stationary side member together with the brake side outer ring 122, numeral 126 indicates a plate spring of, for example, an N-shaped sectional configuration arranged between the cylindrical rollers 125 of each pair, and numeral 129 indicates a friction ring serving as a brake member mounted to the brake-side side plate 123.    Patent Document 1: JP 2003-166555 A    Patent Document 2: JP 2003-97605 A